Abstract: In the air flow control system of a laboratory building module, pressurization of corridors and other residual areas can be maintained neutral in relation to the outdoors by balancing the entire intake or supply flow rate and the entire exhaust rate. The laboratory rooms have various forms of fume hoods whose face velocities at their sash openings is regulated variously, either in response to sash position transducers or in response to face velocity sensors. Fume hoods having two sashes provide two sash-position transducers whose composite output represents the sash opening. A fume hood that relies on sensing of face velocity for correlating its exhaust flow rate with its sash opening utilizes the composite output of multiple face velocity sensors. Exhaust flow rates of fume hoods are regulated so as to increase more rapidly for greater sash openings than for smaller sash openings.

Abstract: In the air flow control system of a laboratory building module, pressurization of corridors and other residual areas can be maintained neutral in relation to the outdoors by balancing the entire intake or supply flow rate and the entire exhaust rate. The laboratory rooms have various forms of fume hoods whose face velocities at their sash openings is regulated variously, either in response to sash position transducers or in response to face velocity sensors. Fume hoods having two sashes provide two sash-position transducers whose composite output represents the sash opening. A fume hood that relies on sensing of face velocity for correlating its exhaust flow rate with its sash opening utilizes the composite output of multiple face velocity sensors. Exhaust flow rates of fume hoods are regulated so as to increase more rapidly for greater sash openings than for smaller sash openings.